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1、How Car Engines WorkIntroduction to How Car Engines WorkHave you ever opened the hood of your car and wondered what was going on in there? A car engine can look like a big confusing jumble of metal, tubes and wires to the uninitiated.You might want to know whats going on simply out of curiosity. Or
2、perhaps you are buying a new car, and you hear things like 3.0 liter V-6 and dual overhead cams and tuned port fuel injection. What does all of that mean? If you have ever wondered about this kind of stuff, then read on - In this article, well discuss the basic idea behind an engine and then go into
3、 detail about how all the pieces fit together, what can go wrong and how to increase performance.The purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. There
4、fore, a car engine is an internal combustion engine - combustion takes place internally. Two things to note: There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on HEMI engines, rotary engines and two-stroke
5、 engines. Each has its own advantages and disadvantages. There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engin
6、e to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we dont see any car
7、s from Ford and GM using steam enginesAlmost all cars today use a reciprocating internal combustion engine because this engine is: Relatively efficient (compared to an external combustion engine) Relatively inexpensive (compared to a gas turbine) Relatively easy to refuel (compared to an electric ca
8、r) These advantages beat any other existing technology for moving a car around. To understand the basic idea behind how a reciprocating internal combustion engine works, it is helpful to have a good mental image of how internal combustion works. One good example is an old Revolutionary War cannon. Y
9、ou have probably seen these in movies, where the soldiers load the cannon with gun powder and a cannon ball and light it. That is internal combustion. Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known a
10、s the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated bellow ,they are: Intake stroke Compression stroke Combustion stroke Exhaust strokeThe piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves, it has the effect of re
11、setting the cannon. Heres what happens as the engine goes through its cycle：1.The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed
12、into the air for this to work. 2.Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful.3.When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving
13、the piston down. 4.Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tail pipe. Then the engine gets ready for the next circle .Cylinders, Displacement and Other Engine PartsThe core of the engine is the cylinder, with the piston
14、 moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline
15、, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing-cost and shape characteristics. These advantages and disadvantages make them more suitable for certa
16、in vehicles. DisplacementThe combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume. The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1,000 cubic centimeters
